Elliptically polarized antenna



June 23, 1953 J. J. NAIL ELLIPTI CALLY POLARIZED ANTENNA 2 Sheets-Sheet1 Filed Feb. 18, 1949 l NVENTO R JAMES J. IVA/L ATTORNEY June 23, 1953 vY J, N 2,643,337

ELLIPTICALLY POLARIZED ANTENNA 7 Filed Feb. 18, 1949 2 Sheets-Sheet 2HO/Z Pam/2471a V1597. pome/znr/a/v HOR. FOL/WEAPON BY M ATTORNEYPatented June 23; I953 ELLIPTICALLY James J. Nail, Basking Ridge, N. Jassignor to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Application February 18, 1949, Serial No.77,137

' 7 Claims. (Cl. 25033.63)

This invention relates to antennas, and more particularly it relates toan antenna with special polarization characteristics. Y

A principal object of the invention is to provide an improved antennawith an elliptically polarized field pattern.

Another object is to provide a novel form of slotted antenna;

Another object is to provide an antenna of the coaxially-fe'd type, andwith an elliptical slot to impart elliptically polarized fieldcharacteristics to the antenna.

A feature of the invention relates to an improved coaxially-fed antennawhich is of simplified and rugged construction, and which has anelliptically polarized field characteristic.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will be best understood by reference to the following descriptionof an embodiment of the invention taken in conjunction with theaccompanying drawings, wherein:

Fig. 1 is a front elevational view of an antenna according to theinvention. i

Fig. 2 is a right-hand elevational view of Fig. 1.

Fig. 3 is a sectional view of Fig. 1 taken along the line 33 thereof andviewed in the direction of the arrows.

Figs. 4 and 5 are respective field pattern diagrams of an antennaaccording to the invention.

The antenna comprises two tubular metal sections I, 2, preferably ofcylindrical metal tubing. These two sections have their adjacentendsci'it at an angle to the longitudinal axis so that when they areassembled in coaxial spaced relationas shown in Figs. 1 and 2, theydefine an elliptical slot 3 of uniform width. This slot is symmetricalaround the common vertical axis of both sections, and the plane of theslot is, for example, at an angle of approximately 25 with respect tothe vertical axis. It will be understood, of course, that the ends ofmembers I and 2 may be cut at any other angle and assembled in coaxialrelation to provide the desired angle a. The two sections can be held inthe proper spaced relation by a pair of insulator spacer elements 4, 5,which can be fastened in any suitable manner to the cooperating adjacentedges of the two sections. Preferably the members 4, 5, should be ofsmall width compared with the diameter of the section I, 2, so as tohave negligible effect on the radiation or field pattern of the finishedantenna.

Welded or otherwise conductively fastened to the inner surface ofsection I is an inverted conical metal member 6 which is positioned sothat its apex is midway between the ends I and 8 of the antenna, and islocated on the central axis of the antenna. A similar conical metalmember 9 is welded or otherwise fastened to the inner periphery of thesection 2, and with its apex closely adjacent the apex of member 6, andin conical alignment therewith. The apex of section 9 is slightlytruncated to leave a circular opening III to which is fastened the endof a small but rigid metal pipe II which can form the outer conductor ofa coaxial feed line. The central inner conductor I2 of this line passesupwardly through the opening I0 and is fastened to the apex of member 6.By this arrangement, therefore, the coaxial feed line can also serve asthe mounting mast for the antenna. If desired one or both ends I, 8, ofthe sections I, 2, can be closed off either by a suitable insulator orby metal cover plates I3.

The antenna, as described, can be used either for transmission orreception of radio waves, and in either case it will have the desiredelliptical polarization field characteristics. 7 Thus Fig. 4 (curve I 4)shows the field characteristics of the antenna as a receiving antennafor horizontally polarized waves at a frequency of 1300 meg-acycles persecond, and curve I5 shows the field characteristics as a receivingantenna for vertically polarized waves. The particular antenna used atthose frequencies had the following dimensions. The over-all length Lwas 0.23 meter, the sections I, 2, had a diameter of 0.04 meter, and theslot 3 had a width of 15 millimeters and was at an angle of degrees withrespect to the central longitudinal axis of the antenna. The conicalsections 6 and 9 each had an altitude of 0.065 meter. It will beunderstood, of course, that these dimensions are given merely by way ofexample, and in no way as a limitation on the scope of the appendedclaims. When the polarization of the waves to be received was variedcontinuously from 0 to it was found that a maximum axial ratio of 2 to 1was obtained. The curves Ma and I5a (Fig. 5) show the field patterns forthe reception respectively of horizontally polarized and verticallypolarized waves at a slightly different frequency of 1275 megacycles persecond.

While I have described the principles of my invention in connection withspecific apparatus, it is to be clearly understood that this descriptionis made only by way of example and not as a limitation to the scope ofmy invention.

What I claim is:

1. An antenna comprising a pair of electrically conductive, cylindricalhollow sections arranged in spaced, end-on coaxial relation, theadjacent ends of said sections terminating in P rallel planes at anacute angle to the axes of said sections to define an elliptical slot,one of said sections being fastened to an inner conductor of a coaxialfeed line and the other section bein connected to the outer conductor ofsaid feed line.

2. An antenna according to claim 1, in which a rigid pipe passescentrally through one antenna section, said pipe constituting the outerconductor of said feed line and having a peripheral flange fastened tothe inner periphery of said one section, the centerconductor of saidfeed line passing out through said pipe, and means connecting the end ofsaid center conductoritothe inner periphery of the other antennasection.

3. An antenna according to claim 2, in which 20 said flange comprises aninverted conical member having its apex fastened to said pipe and itsbase fastened to the inner periphery ofsaid one antenna section. L

4. An antenna according to claim 2 in which the last-mentioned meansincludes a"{ conical member having its apex fastened: 159 5 46 ii tarconductor and its base fastened to theinner periphery ofsaid otherantenna sectioniz 5. An antenna for elliptically polarized patterns,comprising cylindrical tubular" means having an elliptical slotextending substantially entirely around the antenna periphery, and acoaxial feed line" havin h ou er pipe conductor connected tothetlibul'ar me -M o e ide of said si t and the center conduc or conn ced to the tubular incans'on the opposite side of said slot. a; w vk 6.An antennaaccording to claim 5, in which id Ilfigd line 13a?! @r 'g dfiupnpipe conductor hi h act at WWW?! r the n enna ,7; a tfcnnachargingclaim 5, in which aid t s li 11'' a 13 4i cute inenonduc r I o'thecorresponding section b means at a cpn al num r, in has a centerconductor which v v a corresponding section oi. the

a hyrneans" of a conical member.

JAMES J.

Rcierences Cited in the file of this patent 5' cnrrsp STATES PATENTSQwaiiR'R r-E EN S Electronics, $eptemher 1948, pages 103 to 107.

